1. Technical Field
This disclosure relates to a liquid jet head, a method of manufacturing a liquid jet head, and an image forming apparatus.
2. Description of the Related Art
Typically, an image forming apparatus (multi-function machine), which has one or more of the functions of a printer, a facsimile machine, or a copier, forms images (image forming) by conveying a medium (hereinafter also referred to as “sheet” or “paper”) and jetting a liquid (hereinafter also referred to as “recording liquid” or “ink”) onto the conveyed paper by using a liquid jetting apparatus having a recording head (including one or more liquid jet heads) from which liquid (ink) droplets are ejected (jetted). It is to be noted that, although the medium is hereinafter referred to as “sheet” or “paper”, the material of the medium is not to be limited only to those used for manufacturing paper. The medium may include, for example, a paper material, a textile material, a fiber material, a fabric material, a leather material, a metal material, a plastic material, a glass material, a wood material, or a ceramic material. The medium may be, for example, a recording medium (recording paper) or a transfer material (transfer paper). It is to be noted that “image forming” has substantially the same meaning as “recording” or “printing”. For example, “image forming” includes forming images having meaning (e.g. characters, figures, symbols) and also image having no particular meaning (e.g. patterns). Furthermore, the liquid jetting apparatus is for jetting liquid from its liquid jet head and is not limited to an apparatus used for forming images.
One example of the liquid jet head is a piezoelectric type head using a piezoelectric actuator. The piezoelectric type head has a pressure generating part (actuator part) serving as a piezoelectric element for generating pressure to be applied to the liquid (ink) inside a liquid chamber (ink chamber). More specifically, the piezoelectric type head uses layered (laminated) type piezoelectric elements (d33, d31) having a piezoelectric layer and an internal electrode alternately layered on each other. The piezoelectric type head jets liquid droplets by changing the volume/pressure inside its liquid chamber. The volume/pressure inside the liquid chamber is changed by changing the shape of a flexible vibration plate that forms the wall of the liquid chamber. The shape of the vibration plate is changed by displacing the orientation of the layered type piezoelectric elements (d33, d31).
One example of such liquid jet head using layered type piezoelectric elements is disclosed in Japanese Laid-Open Patent Application 8-142325. The layered type piezoelectric element (driving element block) has a piezoelectric layer and an internal electrode layered alternately and an external electrode (individual side) and another external electrode (common side) formed on both ends. Plural driving parts (driving channels) and non-driving parts (on each side) are formed by performing a groove process on the layered type piezoelectric element while leaving a portion thereof remaining. With such configuration, the liquid in the liquid chamber is pressurized by displacing the layered type piezoelectric element d31. Furthermore, a common electrode of the layered type piezoelectric element is removed from the non-driving part on both sides with respect to a direction where the driving parts are arranged.
Furthermore, one example of a liquid jet head using the displacement of the direction of the layered type piezoelectric element d33 is disclosed in Japanese Laid-Open Patent Application No. 2003-250281. In this example, a groove process is performed on piezoelectric elements bonded to a top surface of a base, to thereby form plural piezoelectric elements corresponding to each liquid chamber having communicating nozzles.
Furthermore, Japanese Registered Patent No. 3156411 discloses a line type inkjet head having plural nozzles (opening parts) arranged on a single continuous nozzle plate. The inkjet head has plural piezoelectric elements arranged in correspondence with the nozzles by processing plural bulk piezoelectric members in which the process is performed at the borders of neighboring bulk piezoelectric members.
Furthermore, Japanese Laid-Open Patent Application No. 2000-351217 shows an example where plural liquid jet heads are connected together.
Furthermore, Japanese Laid-Open Patent Application No. 2003-266711 discloses plural head chips, which independently constitute a nozzle actuator, arranged in a line by bonding their sides together.
Furthermore, in Japanese Registered Patent No. 3175449, a head formed by bonding a piezoelectric member to a base member, performing a full-cut slitting process (forming slits reaching the base member), dividing the piezoelectric member into plural piezoelectric elements, and matching the ends of the base member parts.
Furthermore, Japanese Laid-Open Patent Application No. 9-277534 discloses a line type head using no piezoelectric element, and Japanese Laid-Open Patent Application No. 2004-160952 discloses an image forming apparatus having a typical line type head.
Meanwhile, in recent years and continuing, there is a demand for image forming apparatuses (e.g., inkjet recording apparatus) having high speed printing performance. One method of responding to such demand is to increase droplet jetting frequency. However, with this method, such increase of droplet jetting frequency requires a carriage that can correspondingly move at high speed. Thus, a powerful motor is required to be precisely controlled for stably jetting droplets at high frequency.
Another method is to fabricate a line head by extending the length of the head and increasing the number of nozzles provided in the head. However, in order to increase the entire length of the head (such as the above-described head shown in Japanese Laid-Open Patent Application Nos. 8-142325 and 2003-250281), the length of each component constituting the head is to be increased. From the aspects of manufacturing and handling, it is particularly difficult to increase the length of thin long piezoelectric components, such as a lead-zirconate-titanate piezoelectric element.
Although the above-described Japanese Registered Patent No. 3156411 discloses a head having a line type configuration, a piezoelectric element having such configuration is liable to collapse or be chipped away since the piezoelectric element is fabricated by dividing a bulk piezoelectric member. Furthermore, the poor yield of the piezoelectric element increases manufacturing cost.
Furthermore, a line type head having plural liquid jetting heads connected together such as the one shown in the above-described Japanese Laid-Open Patent Application No. 2000-351217 causes the overall size of the head to be considerably large. Such oversized head results in increasing the size of the image forming apparatus.
Furthermore, with the head having plural head chips independently constituting a nozzle actuator by bonding their sides together (as shown in the above-described Japanese Laid-Open Patent Application No. 2003-266711), it becomes difficult, for example, to control the thickness of the adhesive agent layer when attempting to obtain a higher density.
Furthermore, with the head formed by bonding a piezoelectric member to a base member, performing a full-cut slitting process (forming slits reaching the base member), dividing the piezoelectric member into plural piezoelectric elements, and matching the ends of the base member parts (as shown in Japanese Registered Patent No. 3175449), it is to difficult to provide a highly precise pitch between the piezoelectric elements of the adjacent ends of the base member parts.